• 한국재료학회지
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• 제28권9호
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• pp.511-515
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• 2018

W-10 wt% Ti alloys that have a homogeneous microstructure are prepared by thermal decomposition of $WO_3-TiH_2$ powder mixtures and spark plasma sintering. The reduction and dehydrogenation behavior of $WO_3$ and $TiH_2$ are analyzed by temperature programmed reduction and a thermogravimetric method, respectively. The X-ray diffraction analysis of the powder mixture, heat-treated in an argon atmosphere, shows W- oxides and $TiO_2$ peaks. Conversely, the powder mixtures heated in a hydrogen atmosphere are composed of W, $WO_2$ and $TiO_2$ phases at $600^{\circ}C$ and W and W-rich ${\beta}$ phases at $800^{\circ}C$. The densified specimen by spark plasma sintering at $1500^{\circ}C$ in a vacuum using hydrogen-reduced $WO_3-TiH_2$ powder mixtures shows a Vickers hardness value of 4.6 GPa and a homogeneous microstructure with pure W, ${\beta}$ and Ti phases. The phase evolution dependent on the atmosphere and temperature is explained by the thermal decomposition and reaction behavior of $WO_3$ and $TiH_2$.

• 한국분말재료학회지
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• 제14권4호
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• pp.230-237
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• 2007

The fabrication of Fe alloy-40 wt.%TiC composite materials using spark plasma sintering process after ball-milling was studied. Raw powders to fabricate Fe alloy-TiC composite were Fe alloy, $TiH_{2}$ and activated carbon. Fe alloy powder was Distaloy AE (4%Ni-1%Cu-0.5%Mo-0.01%C-bal.%Fe) made by Hoeganes company with better toughness and lower melting point. These powders were ball-milled in horizontal attrition ball mill at a ball-to-powder weight ratio of 30 : 1. After that, these mixture powders were sintered by using spark plasma sintering apparatus for 5 min at $1200-1275^{\circ}C$ in vacuum atmosphere under $10^{-3}$ torr. DistaloyAE-40 wt.%TiC composite was directly synthesized by dehydrogenation and carburization reaction during sintering process. The phase transformation of as-milled powders and sintered materials was confirmed using X-ray diffraction (XRD) and transmission electron microscope (TEM). The density and harness materials was measured in order to confirm the densification behavior. In case of DistaloyAE-40 wt.%TiC composite retained for 5 min at $1275^{\circ}C$, it has the relative density of about 96% through the influence of rapid densification and fine TiC particle reinforced Fe-based composites materials.

• 한국분말재료학회지
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• 제12권5호
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• pp.351-356
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• 2005

Nanoscale Al powder with thin layer of alumina was produced by Wire Electric Explosion (WEE) process. Spark-Plasma Sintering (SPS) was performed for the produced powder to confirm the effectiveness of SPS like so-called 'surface-cleaning effect' and so on. Crystallite size and alumina content of produced powder varied with the ratio of input energy to sublimation energy of Al wire ($e/e_s$): Increase in ($e/e_s$) resulted in the decrease of crystallite size and the increase of alumina content. Shrinkage curve during SPS process showed that the oxide surface layer could not be destroyed near the melting point of Al. It implied that there was not enough or no spark-plasma effect during SPS for Al/Alumina powder.

• 한국세라믹학회지
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• 제39권12호
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• pp.1197-1202
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• 2002

방전 플라즈마 소결법을 이용하여 건전한 강도를 갖는 다공성 육티탄산 칼륨 휘스커 프리폼을 제조하기 위해서, 여러 소결온도 조건하에서 휘스커 프리폼을 제조한 후 기공률과 압축강도 등을 조사하였다. 그 결과, 소결 온도 900∼950${\circ}C$, 유지시간 10분, 압축하중 40 MPa, 승온속도 50${\circ}C$/min, on-off pulse type 12:2의 조건에서 높은 기공률을 갖는 프리폼을 제조할 수 있었다. 이상의 최적조건에서 제조한 프리폼은 기공률이 15∼37% 범위임에도 불구하고 174∼266 MPa의 비교적 높은 압축강도를 나타내었다. 이와 같은 강도의 향상은 휘스커간의 스파크 플라즈마 방전 및 자기 발열작용의 영향에 기인한 것으로 생각된다. 900${\circ}C$ 이하에서 제조한 휘스커 프리폼의 강도 레벨은 80∼100MPa로 900∼950${\circ}C$의 온도조건에서 제조한 프리폼에 비해 2배 이하의 낮은 값을 나타내었다. 1000 ${\circ}C$에서의 압축강도는 523 MPa로 가장 높은 강도값을 나타내었으나, 약 5%의 낮은 기공률을 나타내었다. 이상의 결과로부터, 비교적 강도가 높고 다공성의 티탄산 칼륨 휘스커를 제조하는데 있어 방전 플라즈마 소결법이 효과적인 것으로 생각된다.

• 한국세라믹학회지
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• 제38권6호
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• pp.582-586
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• 2001

방전 플라즈마 소결법을 이용하여 ZrB$_2$-ZrC 복합체를 소결하여 소결 거동과 미세구조에 대하여 조사하였다. 소결 조제로서 란타늄을 첨가하였을 경우에 첨가하지 않았을 경우보다 더 낮은 온도에서 소결 수축이 시작되었으며, 180$0^{\circ}C$에서 거의 치밀화가 완성되었다. 란타늄은 방전플라즈마 소결시 초기 분말 간 액상 형성으로 물질이동을 가속화하여 ZrB$_2$-ZrC 복합체의 치밀화에 커다란 기여를 하며, 냉각 시에 재결정화하여 결정립계와 결정립 삼중점에 란타늄이 포함된 이차상을 형성하는 것으로 확인되었다. 또한 ZrB$_2$-ZrC는 강한 공유결합성 재료임에도 불구하고 미세 구조 내에 잘 발달된 전위 구조를 형성하고 있음을 확인하였다.

• 한국재료학회지
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• 제19권9호
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• pp.504-509
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• 2009

The Zr-based bulk metallic glass matrix composites of a mixture of gas-atomized metallic glass powders and Fe-based nanostructured powders were fabricated by spark plasma sintering. The Fe-based nanostructured powders adopted for the enhancement of plasticity were well distributed in the matrix after consolidation, and the matrix remains as a fully amorphous phase. The successful consolidation of metallic glass matrix composite with high density was attributed to viscous flow in the supercooled liquid state during spark plasma sintering. Unlike other amorphous matrix composites, in which improved ductility could be obtained at the expense of their strength, the developed composite exhibited improvement both in strength and ductility. The ductility improvement in the composite was considered to be due to the formation of multiple shear bands under the presence of the Fe-based nanostructured particles.

• Journal of Advanced Marine Engineering and Technology
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• 제27권1호
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• pp.124-133
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• 2003

Ti-25Al-xNb (x=0, 3, 7, 11, 13 at. %) alloys and 18 vol. % TiB/(Ti-25Al-11Nb) metal matrix composite were fabricated by spark plasma sintering process at 900-120$0^{\circ}C$. Microstructural characteristics of the sintered bodies were identified by SEM, EDX analysis, X-ray diffraction, and differential scanning calorimeterric method. $Ti_3Al$ alloy was consisted of equiaxed $\alpha_2$ phase. $Ti_3Al-Nb$ alloys and the matix of TiB/(Ti-25Al-11Nb) metal matrix composite had the morphology that O phase was precipitated at the grain boundary of $\alpha_2$phase. Volume fraction of O phase and hardness were depended on the concentration of Nb in $Ti_3Al-Nb$ alloy, Rule of mixing could be applied to hardness and Young's modulus of 18 vol. % TiB/(Ti-25Al-11Nb) metal matrix composite.

• 한국분말재료학회지
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• 제15권4호
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• pp.285-291
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• 2008

Fe based ($Fe_{68.2}C_{5.9}Si_{3.5}B_{6.7}P_{9.6}Cr_{2.1}Mo_{2.0}Al_{2.0}$) amorphous powder were produced by a gas atomization process, and then ductile Cu powder fabricated by the electric explosion of wire(EEW) were mixed in the liquid (methanol) consecutively. The Fe-based amorphous - nanometallic Cu composite powders were compacted by a spark plasma sintering (SPS) processes. The nano-sized Cu powders of ${\sim}\;nm$200 produced by EEW in the methanol were mixed and well coated with the atomized Fe amorphous powders through the simple drying process on the hot plate. The relative density of the compacts obtained by the SPS showed over 98% and its hardness was also found to reach over 1100 Hv.

• 한국분말재료학회지
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• 제23권3호
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• pp.195-201
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• 2016

Composite materials consisting of pure aluminum matrix reinforced with different amounts of graphite particles are successfully fabricated by mechanical ball milling and spark plasma sintering (SPS) processes. The shrinkage rates of the composite powders vary with the amount of graphite particles and the lowest shrinkage value is observed for the composite with the highest amount of graphite particles. The current slopes of time increase with increase in the amount of graphite particles whereas the current slopes of temperature show the opposite trend. The highest thermal conductivity is achieved for the composite with the least amount of graphite particles. Therefore, the thermal properties of the composite materials can be controlled by controlling the amount of the graphite particles during the SPS process.

• 한국분말재료학회지
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• 제23권3호
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• pp.213-220
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• 2016

In this study, bulk nickel-carbon nanotube (CNT) nanocomposites are synthesized by a novel method which includes a combination of ultrasonication, electrical explosion of wire in liquid and spark plasma sintering. The mechanical characteristics of the bulk Ni-CNT composites synthesized with CNT contents of 0.7, 1, 3 and 5 wt.% are investigated. X-ray diffraction, optical microscopy and field emission scanning electron microscopy techniques are used to observe the different phases, morphologies and structures of the composite powders as well as the sintered samples. The obtained results reveal that the as-synthesized composite exhibits substantial enhancement in the microhardness and values more than 140 HV are observed. However an empirical reinforcement limit of 3 wt.% is determined for the CNT content, beyond which, there is no significant improvement in the mechanical properties.